Prevention of setup errors in radiotherapy

Patent metadata

Field	Value
Publication number	US-9511243-B2
Application number	US-201314394357-A
Country	US
Kind code	B2
Filing date	Apr 12, 2013
Priority date	Apr 12, 2012
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A patient safety system (PSS) ( 100 ) uses optical tracking in a linear accelerator treatment room to prevent gross setup errors. A patient ( 150 ) undergoes a computed tomography (CT) treatment-simulation scan while a CT ball bearing (BB) is on patient's surface. The CT BB is replaced with an infrared reflective marker (IRRM) ( 160 ) before radiotherapy treatment starts. Coordinates of the CT BB relative to an isocenter of the treatment room are used as reference for tracking. The coordinate system of an optical tracking system is converted to a coordinate system of the treatment room. The PSS evaluates setup accuracy for a radiotherapy session by comparing real-time position of the single IRRM determined by the optical tracking technology with a predicted reference position, and displays results on a graphical user interface. The PSS stops radiation when a deviation between real-time coordinates and predicted coordinates of the IRRM ( 160 ) exceeds a predefined threshold.

First claim

What is claimed is:

1. A method, with a computer, of tracking changes in position of a patient while the patient is undergoing radiotherapy, comprising:
placing a computed tomography ball bearing (CT BB) at a location on a surface of one of a face mask and an immobilization device for a patient;
performing a treatment-simulation computed tomography scan of the patient;
calculating, with a computer ( 110 ), coordinates of the CT BB, based on the treatment-simulation computed tomography scan of the patient;
removing the CT BB from the surface of the one of a face mask and an immobilization device;
placing an infra-red reflecting marker (IRRM) ( 160 ) at the location of the one of a face mask and an immobilization device;
storing, in a database ( 212 ) communicatively coupled to the computer, the coordinates of the CT BB as predicted coordinates of a predicted location of the IRRM; and
while the patient is receiving radiotherapy with a linear accelerator:
determining a real-time location of the IRRM,
comparing, with the computer, the real-time location of the IRRM with the predicted location of the IRRM, and
displaying results of the comparing in a graphical user interface ( 500 ) of a display ( 174 ) communicatively coupled to the computer.

2. The method of claim 1 , wherein the step of comparing continually compares the real-time location of the IRRM with the predicted location of the IRRM at a rate of 15 Hz, and wherein the step of displaying continually updates the results of the comparing at the rate of 15 Hz.

3. The method of claim 1 , including the step of:
setting a tolerance for a deviation between the real-time location of the IRRM and the predicted location of the IRRM.

4. The method of claim 3 , including the step of:
activating an alarm when the deviation between the real-time location of the IRRM and the predicted location of the IRRM is greater than the tolerance.

5. The method of claim 4 , wherein the computer is communicatively coupled to the linear accelerator, and including the step of:
shutting off radiation from the linear accelerator when the deviation between the real-time location of the IRRM and the predicted location of the IRRM is greater than the tolerance.

6. The method of claim 3 , wherein the computer is communicatively coupled to the linear accelerator, and including the step of:
shutting off radiation from the linear accelerator when the deviation between the real-time location of the IRRM and the predicted location of the IRRM is greater than the tolerance.

7. The method of claim 1 , wherein the step of calculating uses a first coordinate system of the treatment-simulation computed tomography scan.

8. The method of claim 7 , wherein the step of using includes using an optical tracking system ( 101 ), communicatively coupled to the computer, to optically determine real-time coordinates of the real-time location of the IRRM based on infra-red light reflections ( 123 and 125 ) from the IRRM sensed by cameras ( 121 and 122 ) of the optical tracking system, wherein the optical tracking system uses a second coordinate system.

9. The method of claim 8 , including a step of converting the second coordinate system of the optical tracking system to the first coordinate system of the treatment-simulation computed tomography scan.

10. The method of claim 9 , wherein the step of comparing includes comparing, with the computer, the real-time coordinates of the IRRM with the predicted coordinates of the IRRM.

11. The method of claim 10 , wherein the step of comparing continually compares the real-time coordinates of the IRRM with the predicted coordinates of the IRRM at a rate of 15 Hz, and wherein the step of displaying continually updates the results of the comparing at the rate of 15 Hz.

12. The method of claim 11 , including the step of:
defining a deviation between optically-determined real-time coordinates of the IRRM and the predicted coordinates of the IRRM as a quadrature sum of deviations along all three dimensions of the optically-determined real-time coordinates of the IRRM compared to the predicted coordinates of the IRRM.

13. The method of claim 12 , including the step of:
setting a tolerance for the deviation between the optically-determined real-time coordinates of the IRRM and the predicted coordinates of the IRRM.

14. The method of claim 13 , including the step of:
activating an alarm when the deviation is greater than the tolerance.

15. The method of claim 14 , wherein the computer is communicatively coupled to the linear accelerator, and including the step of:
shutting off radiation from the linear accelerator when the deviation is greater than the tolerance.

16. The method of claim 13 , wherein the computer is communicatively coupled to the linear accelerator, and including the step of:
shutting off radiation from the linear accelerator when the deviation is greater than the tolerance.

17. A method, with a computer, of tracking changes in position of a patient while the patient is undergoing radiotherapy, comprising:
placing a computed tomography ball bearing (CT BB) at a location on a surface of a patient;
performing a treatment-simulation computed tomography scan of the patient;
calculating, with a computer ( 110 ), coordinates of the CT BB, based on the treatment-simulation computed tomography scan of the patient;
removing the CT BB from the surface of the patient;
making a tattoo on skin of the patient at the location of the CT BB;
placing an infra-red reflecting marker (IRRM) ( 160 ) at the location of the tattoo;
storing, in a database ( 212 ) communicatively coupled to the computer, the coordinates of the CT BB as predicted coordinates of a predicted location of the IRRM; and
while the patient is receiving a first session of radiotherapy with a linear accelerator:
determining a real-time location of the IRRM,
comparing, with the computer, the real-time location of the IRRM with the predicted location of the IRRM, and
displaying results of the comparing in a graphical user interface ( 500 ) of a display ( 174 ) communicatively coupled to the computer.

18. The method of claim 17 , including the steps of:
removing the IRRM from the location of the tattoo on the skin of the patient after completion of the first session of radiotherapy;
maintaining the tattoo on the skin of the patient until occurrence of at least one additional session of radiotherapy subsequent to the first session of radiotherapy; and
placing an IRRM at the location of the tattoo prior to start of the at least one additional session of radiotherapy.

19. The method of claim 18 , including the step of retrieving, with the computer, from the database the coordinates of the CT BB as the predicted coordinates of the predicted location of the IRRM.

20. The method of claim 19 , including, while the patient is receiving the at least one additional session of radiotherapy with the linear accelerator:
determining the real-time location of the IRRM,
comparing, with the computer, the real-time location of the IRRM with the predicted location of the IRRM, and
displaying results of the comparing in the graphical user interface of the display.

Assignees

• Univ Florida

Inventors

• Yan Guanghua
• Lu Bo
• Liu Chihray
• Li Jonathan G

Classifications

• A61N2005/1051

  using an active marker · CPC title

• A61N5/1049

  for verifying the position of the patient with respect to the radiation beam · CPC title

• A61B6/583

  using calibration phantoms · CPC title

• G01S17/48

  Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves · CPC title

• A61N5/107

  in real time, i.e. during treatment · CPC title